Glaucomatous optic neuropathy is a complex process with multiple underlying risk factors. For Decades, this disease was mainly attributed to elevated intraocular pressure (IOP) and hence, the majority of current managements focuses on reducing this pressure. More recently attention has been turning towards other risk factors, particularly towards the perfusion and blood supply of the optic nerve head. Several recent studies correlated a low perfusion pressure or nocturnal hypotension with the diagnosis or the progression of glaucoma.